Background & Management

Definition

 

Displacement of proximal femoral epiphysis in the immature hip

- due to imbalance of mechanical and endocrine factors 

 

Epidemiology

 

M 12-14

F 11-13

 

3 / 100 000

- male predominance

- L > R

 

High in Polynesians and African - Americans

- 7% risk to second family member

 

Bilateral SUFE

 

No endocrine abnormality

- 20% at time of of diagnosis

- another 20% during diagnosis

- up to 60% with long term follow up

 

Endocrine abnormality

- up to 75%

 

Aetiology

 

Predisposing factors

- obesity / height

- rapid growth

- endocrinopathies 

 

1. Mechanical

 

A.  Weight / Height

- 50% over 95th percentile weight

- 50% over 97th percentile height

 

B.  Growth plate

- widened zone of hypertrophy

- increased slope

- increased retroversion Southwick angle > 14o

- assess other side

- if very retroverted is indication to prophylactic pinning

 

2.  Endocrine

 

Imbalance of

- Testosterone - causes physeal fusion

- Growth hormone - causes physeal hypertrophy / weakens

 

Causes

- hypothyroidism

- renal rickets

- hypopituitary

- acromegaly

- CRF

 

3.  Other

 

Marfan's / Downs / Klinefelter's

Chemo therapy / DXRT

GH

 

Pathology

 

Widened hypertrophic zone 

- constitutes 60% of physeal width

 

Abnormality of Hypertrophic & Proliferative Zones

- failure occurs in this zone at junction with proliferative zone

- disordered chondrocyte columns

- decreased number of cells

- cells smaller

- increased number of dead and degenerative cells

 

Head remains in acetabulum via L. Teres

- neck displaces anterosuperior on physis and ER

- head slips posterior / inferior on neck

 

Classification

 

Chronological

 

Acute < 3/52 symptoms

Acute on Chronic 

Chronic >3/52

 

Morphological 

 

Southwick Slip angle

- lateral X-ray  / frogs legs

- epiphyseal-shaft angle 

- abnormal angle minus normal angle 

- <30° / 30- 50 / >50°

- mild / moderate / severe

 

Stability

 

Loder JBJS 1993

 

Stable 

- able to able to weight / 0% AVN

 

Unstable 

- unable to weight bear / 50% AVN

 

History

 

Overweight adolescent boy hip or knee pain

 

Examination

 

Limps

Walk with ER (chronic)

Flexes into Abduction / ER

Limitation IR / Abduction

LLD (real and apparent)

 

X-ray

 

AP

 

SUFE AP

 

Trethowan Line / Kleins Line

- line along superior neck usually transects 20% head

 

Widened physis

 

Inferomedial remodelling in chronic slip

 

Frog Leg Laterals / Shoot through lateral

 

SUFE Lateral

 

Shoot through lateral

- best to avoid frog leg lateral as may displace slip

 

Posteriorly displaced & angulated

 

Measure Southwick Angle

- calculate severity of slip

- also estimates risk of slip of other side / looking for retroversion

 

Management

 

Aims

 

1.  Prevent further slip / obtain physis fusion

- 30% will continue untreated

 

2   Prevent deformity and OA

- MUA / ORIF / osteotomy

 

3.  Avoid complications 

 

Algorithm

 

Dr Deborah Eastwood

APOS 2008

Greater Ormond St, London

 

1.  True acute / unstable

- < 24 hours

- treat like fracture

- "inadvertent" correction

 

2.  Pin in situ

 

3.  Severe slip / unable to pin in situ

- refer tertiary pediatric hospital

- wait 3/52, traction

- intracapsular ostetomy

 

4.  Moderate - severe deformity post fusion

- refer for osteotomy

 

In Situ Pinning

 

Gold Standard

- supine on bed / traction table

- avoid reduction / allowed some minor, non forceful internal rotation

- entry on anterior femoral neck to get into posteriorly displaced physis

- central placement in head crossing physis

- 5 threads crossing physis

- single screw in central location with satisfactory fixation avoiding joint penetration

- approach & withdrawal X-ray to ensure no joint penetration

- +/- pin other side

 

CT post operatively

- ensure no screw protrusion

 

TWB 6/52

 

Serial Xray

- ensure epiphysis doesn't grow off screw

- screw can break / can lose position

- observe til physis closes

- no indication to remove pin

 

Results

 

Weinstein et al JBJS Am 1991

- 40 year follow up of 155 hips

- some pinned in situ / some realigned / some reduced

- rates of OA / AVN / chondrolysis increased with severity of slip

- rates of OA / AVN / chondrolysis increased with reduction / realigned

- regardless of severity of slip, pinning in situ had best results with lowest complications

 

Closed Reduction Prior to Pinning

 

Disadvantage

 

Traditionally associated with higher risk AVN

 

Advantage

 

Theorectical

- may decrease AVN in severe, unstable hips

- prevent severe deformity / late OA

 

Indication

 

Acute & unstable < 24 hours

 

Results

 

Peterson et al J Paediatr Orthop 1997

- 91 cases of severe, acute, unstable slips

- 42 closed reduction < 24hrs AVN 7%

- 49 closed reduction > 24hrs AVN 20%

- hypothesised that had acute obstruction of epiphyseal vessels 

- timely decompression allows revascularisation

- treat an acute unstable slip as per a fracture

- these have up to 50% AVN rate anyway

- emergency operation

 

Chen et al J Paediatr Orthop 2009

- 30 acute, unstable slips

- 25 closed reductions and 5 open reductions with release hematoma

- 4 cases of AVN

 

Open Reduction Prior to Pinning

 

Indications

- severely displaced slips

 

Reasoning

- moderate or severe slips do poorly in long term

- best treatment is intra-capsular reduction or osteotomy

- risk AVN either way

- acute open reduction easier

- also decompress hip

 

Technique Subcapital Osteotomy

- trochanteric slide osteotomy / Ganz Osteotomy / digastric osteotomy

- anterior capsulotomy

- Z shaped to preserve superior vessel along neck) along anterior acetabulum and inferior neck

- capsule banana skinned off neck

- epiphysis taken off neck, still attached to capsule

- neck debrided to avoid tensioning of posterior vessels

- head replaced and pinned as per normal

 

Results

 

Slongo and Ganz et al Oper Orthop Traumatol 2007

- 30 cases of acute slip treated with subcapital osteotomy

- no cases of AVN

 

Prophylactic Pinning

 

Issues

 

Can justify but may cause complications 

- i.e. chondrolysis, subtrochanteric fracture secondary to screw

 

Incidence bilateral slips

- unknown

- may be > 35%

- high incidence of asymptomatic and mild contralateral slips

 

Major indications

- young

- unreliable

- geographic isolation

- endocrine

 

Technique of Pin in Situ

 

Set up

 

1.  Supine on radiolucent table

- very easy to set up

- much faster if pinning both sides / reduced set up

- theoretical risk of displacing slip / inadvertant manipulation

- lateral by flexing and full ER of hip / frog legs

 

2.  Traction Table

- easy to get AP and lateral

- need 2 set ups for bilateral pinning

- takes longer in this regard

 

Technique

 

Draw anterior and lateral lines

- get AP, draw line mark using radiopague ruler to centre of head

- get lateral, repeat

- intersection of points is incision site

 

Stab incision

- guide wire percutaneously to neck

- more anterior entry point on femoral neck required the more the epiphysis is displaced posteriorly

- central in head on both views

- ensure don't penetrate head

- cannulated drill

- 7 mm screw

- 8-10 mm or 4-5 threads across physis

- do far and away screening / approach withdraw

- this ensures screw is not in joint